This invention relates to semisubmerged water surface navigation ships and more particularly to a water surface navigation ship comprising lower hulls normally submerged below the water surface, an upper hull normally above the water surface, and water breakers connecting the lower hulls and the upper hull and being normally afloat on the water surface.
The history of ships and shipbuilding shows only slight changes basically from ancient times to the present time. That is, all ships including ancient dugout log canoes and huge modern vessels become afloat by the principle of buoyancy arising from the displaced water. The use of propellers in the place of sails and oars may be one of the small changes in the history of shipbuilding.
The widespread appearance of submerged ships in this century was a big revolution in ship building technology, although they are used mostly for military purposes. The characteristics of a submerged ship are as follows.
1. The main resistances of water against surface floating ship propulsion are frictional resistance and wave-making resistance. When the speed of the ship is increased, the wave-making resistance becomes greater. As there is no wave-making resistance for submerged ships, an absolute advantage exists for high-speed navigation of a submerged ship.
2. As a submerged ship submerges under water, it is not subject to any influence of waves, wind, etc. Therefore no rolling or pitching motion occurs.
3. As a submerged ship submerges under water, it cannot use engines which consume oxygen from the air. Instead, it must use non-oxygen type engines such as battery engines, nuclear power engines, etc.
4. As a submerged ship submerges under water, it has no reserve buoyancy, so it needs a special lifting/diving system such as water ballasting equipment or lifting/diving plates in order to navigate or lie to with ample stability.
The ever continuing goal of shipbuilding technology is to produce "faster, stabler, safer and more economical" ships. It is only 100 years since ships were constructed by modern shipbuilding technology. In order to reach the above goal, higher power engines are installed for higher speed, greater breadth and length of ship hulls are designed for stabler ships with less rolling and pitching, greater reserve buoyancy is added for safety, and greater dead weight is sought for economy.
However, no matter how high the power of an engine may be for higher speed, the wave-making resistance owing to surface waves increases in a geometric progression, and thus the speed of a ship cannot exceed a certain limitation. No matter how large the breadth and length of ship hull may be for the purpose of attaining stability, the ship cannot avoid the effect of waves and wind as long as it is afloat on the water surface. Recently, devices such as stabilizers have been used for this purpose, but as the ship hull becomes bigger, its reserve buoyancy becomes greater, and thus the added buoyancy becomes large which makes it difficult to control the motion of ship by means of such devices. The appearance of submerged ships has solved these problems in shipbuilding technology. For example, a water surface navigation ship of 30,000 DWT cannot use stabilizers or underwater horizontal rudders or plates to control the rolling or pitching owing to change of buoyancy because of the excessively great change in the buoyancy induced by waves and/or wind. In contrast, a fully submerged ship of 30,000 DWT has no reserve buoyancy and no buoyancy change capacity, and therefore horizontal rudders or plates with the minimum lifting/diving capacity can control the motion of the ship.
As is well known, recent rapid transportation of cargo is being done more by aircraft than by ship. This is because marine transportation by ship takes a longer time, cargo can be damaged on account of rough weather during transportation, the loading and unloading of massive ship cargo are troublesome and apt to cause damage, and their custom work takes a longer time.
In general port operation, crane work is carried out twice, i.e., one for loading and unloading of cargo and the other is for sorting the cargo. The first crane work is time consuming and costly but is not performed for sorting which is carried out afterwards and separately. No matter how inexpensive marine transportation may be, it must lose the major role in transportation as long as air transportation can provide fast, safe and punctual door-to-door deliveries.